WHAT IS THE IDEAL RATE OF FERTILITY?

When the study first kicked off in 1950, there were no shrinking populations in any country around the world.

If fertility is sustained over a long period, each generation would replace itself exactly without any need for the country to balance the population.

Speaking to the BBC, Prof Christopher Murray, the director of the Institute for Health Metrics and Evaluation at the University of Washington and report author said: “We’ve reached this watershed where half of countries have fertility rates below the replacement level, so if nothing happens the populations will decline in those countries. It’s a remarkable transition.

“It’s a surprise even to people like myself, the idea that it’s half the countries in the world will be a huge surprise to people.”

WHICH COUNTRIES ARE MOST AFFECTED?

ECONOMICALLY developed countries including most of Europe, the US, South Korea and Australia are currently facing a baby bust more than less developed countries.

The population in these countries is not falling, however, due to the migration. It can also take a generation for changes in fertility rates to take hold.

But Professor Murray believes economically developed countries will start to see population rates changing in the near future.

He said: “We will soon be transitioning to a point where societies are grappling with a declining population. “Half the world’s nations are still producing enough children to grow, but as more countries advance economically, more will have lower fertility rates.”

WHERE ARE WOMEN HAVING THE MOST CHILDREN?

WOMEN in Niger, West Africa have an average of 7.1 while women in Chad have 6.7.

In Somalia, Mali and Afghanistan, women are having between 6 and 6.1, while in South Sudan, Burkina Faso, Burundi, Uganda and Angola, women are having between 5.1 and 5.9.

WHERE ARE WOMEN HAVING THE LEAST CHILDREN?

CYPRUS and Taiwan have the lowest fertility rates in the world with the average woman having one child. In South Korea, Andorra, Puerto Rico and Thailand, the average is 1.2.

While in Bosnia and Herzegovina, Poland, Moldova and Japan, women have an average of 1.3 children.